Question: Solve for $r$ : $2 + r = 17$
Answer: Subtract $2$ from both sides: $ \begin{eqnarray} \\ 2 + r &=& 17 \\ \\ {-2} && {-2} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{2 + r} &\hphantom{=}& \hphantom{17} \\ r &=& 17 {- 2} \\ \end{eqnarray} $ Simplify. $ r = 15$